The present invention generally relates to motor drivers and more particularly, a circuit with motor driver spike suppression.
Motor driver integrated circuits typically have an absolute maximum rating limit for the spike between ground and the output switching node to a voltage between −2V and −5V. Spiking may be generated by gate drive inductance and high dv/dt gate drive.
One approach to reduce spike levels is to place MOSFETS close to the driver which reduces the gate drive inductance. Referring to FIG. 1, a motor driver circuit 100 is shown. The circuit 100 shows a microchip 110 supplying high side gating (TG) and low side gating (BG) signals to a high side MOSFET 120 and a low side MOSFET 130. However, mechanical restrictions on MOSFET locations may require the MOSFETS to be separated from the driver. For example, MOSFETs 120 and 130 may need to be distanced from the driver because of thermal restrictions. The separation of MOSFETs from the driver may cause the gate drive distance to increase to a length that will cause a spike that exceeds the driver part ratings. Referring to FIG. 2, an example measurement of high side floating offset voltage output from the circuit 100 is shown. The minimum value of undershoot from this measurement is approximately negative 7.2 volts.
As can be seen, there is a need for a motor driving circuit that can employ MOSFETs while suppressing spiking levels.